﻿
//预处理名称，详情见：https://www.runoob.com/csharp/csharp-preprocessor-directives.html
#define PI

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace PreprocessorDAppl {
    internal class Program {
        static void Main(string[] args) {

            #if (PI) //这里为true，因为上面定义的 define 就是等于PI
            Console.WriteLine("PI is defined");
            #else
            Console.WriteLine("PI is not defined");
            #endif
            Console.ReadKey();

        }
    }
}
